FIG. 1.

Results of E. coli lacZ gene TaqMan assay performed on DNAs extracted from broth cultures of the E. coli O157:H7 Odwalla strain using the Xtra Amp tube, Isocode paper, and PrepMan matrix reagents. Thirty microliters (out of 100 μl) of an overnight culture pellet was extracted with the Xtra Amp and PrepMan reagents, and 10 μl was extracted with the Isocode paper. Fifty microliters of the PCR master mix plus 5 μl of Amp Enhance solution were used in the Xtra Amp tube. For the other two methods, 5- and 1-μl aliquots of the PrepMan-extracted DNA and 20- and 5-μl aliquots of Isocode paper-extracted DNA were used as the templates. Fluorescence readings for the 6-carboxyfluorescein reporter dye were obtained after 43 cycles of PCR, were corrected for background, and are plotted on the y axis. Δ Fluorescence, change in fluorescence.